1. Field of the Invention
It is well known that molybdenum compounds added to lubricating oils, depending on their structure, can play a significant role as both friction modifiers and as anti-wear additives. The present invention is related to lubricating oil additives and lubricant compositions, and more particularly to a novel class of molybdenum-based friction modifier additives derived from organo-imido molybdenum complexes that can be incorporated into lubricating oils. The purpose of the present invention is to provide additives that can reduce friction and aid formulators of engine oils to meet new requirements for passenger car motor oils, such as ILSAC GF-3.
2. Description of Related Art
Regulatory agencies today are seeking to improve the fuel economy of motor vehicles through legislation (CAFE requirements) that puts the responsibility for achieving such economy on the motor vehicle manufacturers, who in turn transfer at least a portion of this responsibility to lubricant oil manufacturers by means of engine oil specifications. As these fuel economy requirements become more and more rigorous, it becomes more and more important to incorporate friction modifier additives into lubricant compositions. It is well known that the fuel efficiency of engine oils can be improved by using friction reducing additives. It is also well understood that these additives must be active at engine operational temperature in order to be most effective.
In addition, zinc dialkyldithiophosphates (ZDDP) have been used in formulated oils as antiwear and antioxidant additives for more than 50 years. However, zinc dialkyldithiophosphates give rise to ash, which contributes to particulate matter in automotive exhaust emissions. Regulatory agencies are seeking to reduce emissions of zinc into the environment. Moreover, the phosphorus present in the dialkyldithiophosphates is also suspected of limiting the service life of catalytic converters that are used on vehicles to reduce pollution. It is important to limit the particulate matter and pollution formed during engine use for toxicological and environmental reasons, but it is also important to maintain undiminished the antiwear properties of the lubricating oil. In view of the aforementioned shortcomings with the known zinc- and phosphorus-containing additives, it is a further object of this invention to provide antiwear additives that contain neither zinc nor phosphorus.
In developing lubricating oils, there have been many attempts to provide additives that impart antifrictional or oiliness properties. Molybdenum compounds are known to be useful as friction modifiers and antioxidants and to be capable of providing antiwear and extreme pressure resistance properties in lubricating oil compositions.
Thiocarbamate additives for lubricating oils, particularly molybdenum-containing thiocarbamates, have been disclosed in the patent literature.
U.S. Pat. No. 3,419,589 discloses a process for the preparation of molybdenum (VI) dialkyldithiocarbamate complexes and sulfurized derivatives thereof in substantially high yields by the dilute nitric acid acidification of alkali dialkyldithiocarbamates and alkali molybdates and the subsequent treatment thereof with hydrogen sulfide to form the sulfurized derivatives of the reaction product. These compounds are said to be useful as additives for lubricants.
U.S. Pat. No. 3,509,051 discloses lubricating oils and greases that are said to exhibit excellent extreme pressure, antioxidant, and wear properties when they contain sulfurized oxymolybdenum dithiocarbamates of the general formula:[R2N—CS—S—]2Mo2OmSn,where m+n=4, m is in the range of 2.35 to 3, n is in the range of 1.65 to 1, and R is a hydrocarbon group having 1 to 24 carbon atoms.
U.S. Pat. No. 3,541,014 discloses lubricant compositions that are said to have improved extreme pressure capabilities and antiwear properties, which are characterized by the presence therein of oil-soluble molybdenum-containing organic complexes. These complexes are produced by contacting molybdenum-containing anions with oil-soluble overbased, Group II metal-containing compositions until a portion of the anions reacts with the Group II metal. Lubricating oils, cutting oils, greases, and the like are illustrative of the lubricant compositions disclosed.
U.S. Pat. No. 4,098,705 discloses a compound of the formula:
wherein R1 and R2 stand for a hydrocarbyl group having 1 to 24 carbon atoms and x is a number of 0.5-2.3 that is said to be useful as an additive for lubricants.
U.S. Pat. No. 4,164,473 discloses hydrocarbon-soluble organo molybdenum complexes obtained as the reaction product of a hydrocarbyl substituted hydroxy alkylated amine, e.g., N,N′,N′-tris(2-hydroxy ethyl)-n-tallow-1,3-diaminopropane, with about one molar equivalent of a molybdenum compound, e.g., ammonium molybdate, that are said to be useful hydrocarbon additives particularly in combination with an oil-soluble sulfur donor, e.g., a metal dialkyl dithiophosphate to provide an additive combination for lubricating oils. Lubricating compositions comprising these coadditives are disclosed to exhibit improved antifriction and antiwear properties.
U.S. Pat. No. 4,259,194 discloses antioxidant additives for lubricating oil that are prepared by combining ammonium tetrathiomolybdate and a basic nitrogen compound complex to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,259,195 discloses antioxidant additives for lubricating oil that are prepared by combining a polar promoter, an acidic molybdenum compound, and certain basic nitrogen compounds to form a molybdenum-containing composition.
U.S. Pat. No. 4,263,152 discloses the preparation of antioxidant additives for lubricating oil by combining water, an acidic molybdenum compound, a basic nitrogen compound complex and a sulfur source to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,265,773 discloses antioxidant additives for lubricating oil that are prepared by combining an acidic molybdenum compound, an oil-soluble basic nitrogen compound, and carbon disulfide to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,266,945 discloses the preparation of molybdenum-containing compositions by the reaction of an acid of molybdenum or a salt thereof, phenol or aldehyde condensation product therewith, and a primary or secondary amine. The preferred amines are diamines such as tallow-substituted trimethylene diamine and their formaldehyde condensation products. An optional but preferred ingredient in the reaction mixture is at least one oil-soluble dispersant. The molybdenum-containing compositions are said to be useful as additives in fuels and lubricants, especially so in lubricants when combined with compounds containing active sulfur.
U.S. Pat. No. 4,272,387 discloses antioxidant additives for lubricating oil that are prepared by combining an acidic molybdenum compound, a basic nitrogen compound complex, and a sulfur source to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,283,295 discloses antioxidant additives for lubricating oil that are prepared by combining a polar promoter, ammonium tetrathiomolybdate, and a basic nitrogen compound complex to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,285,822 discloses antioxidant additives for lubricating oil that are prepared by (1) combining a polar solvent, an acidic molybdenum compound, and an oil-soluble basic nitrogen compound to form a molybdenum-containing complex and (2) contacting said complex with carbon disulfide to form a sulfur- and molybdenum-containing composition.
U.S. Pat. No. 4,289,635 discloses molybdenum-containing compositions that are prepared by reacting an olefinically unsaturated compound capable of reacting with active sulfur with a composition prepared by reacting:
(a) a phosphorus-containing acid represented by the formula:
wherein each X and X′ is independently oxygen or sulfur, each n is zero or one and each R is independently the same or a different hydrocarbon-based radical; and(b) at least one hexavalent molybdenum oxide compound, and(c) hydrogen sulfide, in the presence of (d) a polar solvent. It is said that the compositions are useful as additives for lubricants and that internal combustion engines exhibit improved fuel economy when lubricated with them.
U.S. Pat. No. 4,315,826 discloses multipurpose lubricant additives that are prepared by reaction of carbon disulfide with thiomolybdenum derivatives of polyalkenylsuccinimides having basic nitrogen functions. It is said that the subject additives function as dispersants possessing excellent antifriction properties and impart antiwear and antioxidant properties to a lubricant.
U.S. Pat. No. 4,369,119 discloses antioxidant additives for lubricating oil that are prepared by combining (a) a sulfur-containing molybdenum compound prepared by reacting an acidic molybdenum compound, a basic nitrogen compound, and a sulfur compound, with (b) an organic sulfur compound.
U.S. Pat. No. 4,370,246 discloses the preparation of an antioxidant additive combination for lubricating oils by combining (a) a sulfur containing molybdenum compound prepared by reacting an acidic molybdenum compound, a basic nitrogen compound, and a sulfur compound, with (b) an aromatic amine compound.
U.S. Pat. No. 4,395,343 discloses antioxidant additives for lubricating oil that are prepared by combining (a) a sulfur containing molybdenum compound prepared by reacting an acidic molybdenum compound, a basic nitrogen compound, and carbon disulfide, with (b) an organic sulfur compound.
U.S. Pat. No. 4,402,840 discloses antioxidant additives for lubricating oil that are prepared by combining (a) a sulfur containing molybdenum compound prepared by reacting an ammonium thiomolybdate compound, and a basic nitrogen compound, with (b) an organic sulfur compound.
U.S. Pat. No. 4,428,848 discloses compounds prepared by the reaction of an adduct of a phosphosulfurized polyisoalkylene or alpha olefin with an acidified hexavalent molybdenum salt which is said to give enhanced copper corrosion protection relative to the non-molybdenum treated adducts when incorporated in lubricants. Also disclosed is the combination of such compounds with a zinc dialkyldithiophosphate, which combination imparts to lubricants an oxidation inhibition that is said to be greater than is obtainable with either the zinc dialkyldithiophosphate or the molybdenum-containing adduct alone.
U.S. Pat. No. 4,474,673 discloses antifriction additives for lubricating oil that are prepared by reacting a sulfurized organic compound having an active hydrogen or potentially active hydrogen with a molybdenum halide.
U.S. Pat. No. 4,479,883 discloses a lubricating oil composition that is said to have particularly improved friction reducing properties that comprises an ester of a polycarboxylic acid with a glycol or glycerol and a selected metal dithiocarbamate and that contains a relatively low level of phosphorus.
U.S. Pat. No. 4,501,678 discloses a lubricant containing molybdenum dialkyldithiocarbamates that is said to be useful for improving the fatigue life of gears.
U.S. Pat. No. 4,765,918 discloses a lubricating oil additive prepared by reacting a triglyceride with a basic nitrogen compound to form a reaction product, reacting the reaction product with an acidic molybdenum compound to form an intermediate reaction product, and reacting the intermediate reaction product with a sulfur compound.
U.S. Pat. No. 4,889,647 discloses molybdenum complexes prepared by reacting (a) a fatty oil, (b) diethanolamine, and (c) a molybdenum source. The complexes are said to impart antifriction and antiwear properties to lubricating compositions and to decrease fuel consumption in internal combustion engines.
U.S. Pat. No. 4,995,996 discloses a lubricating composition comprising a major amount of an oil of lubricating viscosity and a minor amount of an additive having the formula Mo2L4 wherein L is a ligand selected from xanthates and mixtures thereof and, in particular, xanthates having a sufficient number of carbon atoms to render the additive soluble in the oil. In general, the xanthate ligand, L, will have about 2 to 30 carbon atoms.
U.S. Pat. No. 5,605,880 discloses a lubricating oil composition which is obtained by containing in (A) a base oil in which the content of the aromatic ingredients is 3.0% by weight or less, N is 50 ppm by weight or less, S is 50 ppm by weight, and the viscosity is 2.0-50.0 mm2/s, based on the total weight of the composition, (3) 0.05-2.0% by weight of alkyldiphenylamine(s) and/or phenyl-α-naphthylamine(s) and (C) MoDTC of C8-23 and/or C3-18 in an amount of 50-2,000 ppm by weight in terms of the amount of molybdenum. Such a lubricating oil composition is said to have high heat-resistant properties, a high stability to oxidation, and improved friction characteristics, and is suitably used especially as a lubricating oil for internal combustion engines.
U.S. Pat. No. 5,650,381 discloses a lubricating oil composition which contains from about 100 to 450 parts per million of molybdenum from a molybdenum compound which is substantially free of active sulfur and about 750 to 5,000 parts per million of a secondary diarylamine. This combination of ingredients is said to provide improved oxidation control and friction modifier performance to the lubricating oil. The composition is particularly suited for use as a crankcase lubricant. (See, also, U.K. 2,307,245.)
U.S. Pat. No. 5,688,748 discloses a lubricating oil composition for internal combustion engines which is said to have high resistance to oxidation by nitrogen oxides, excellent friction characteristics that is maintained for a prolonged period, and the ability to reduce the fuel consumption for a prolonged period. The lubricating oil composition consists of a base oil principally consisting of a hydrocarbon oil which has a dynamic viscosity of 2-20 mm2/s at 100° C. and contains 3 wt % or less aromatic components in total, 45 wt % or more one- and two-ring naphthenes in total, 50 wt ppm or less sulfur and 50 wt ppm or less nitrogen, to which are added, with respect to the total weight of the composition, 0.02-0.2 wt % as molybdenum of molybdenum dithiocarbamate, 0.02-0.15 wt % as phosphorus of zinc dithiophosphate, and 0.05-3 wt % of phenol-based antioxidant. The lubricating oil composition is said to have a low friction coefficient, which is maintained for a prolonged period even after oxidation by nitrogen oxides.
U.S. Pat. No. 5,840,672 discloses antioxidant compositions comprising (A) at least one secondary diarylamine, (B) at least one sulfurized olefin and/or sulfurized hindered phenol, and (C) at least one oil soluble molybdenum compound. These antioxidant compositions are said to be highly effective at providing oxidative stability to lubricating compositions, especially for highly saturated, low sulfur lubrication base oils.
U.S. Pat. No. 6,103,674 discloses a lubricating oil additive that comprises the reaction product of:
(a) an unsaturated or saturated ester or acid,
(b) a diamine of the formula:

(c) carbon disulfide, and
(d) a molybdenum compound,
wherein R8 is an alkyl group of 1 to 40 carbon atoms, R9 and R10 are independently selected aliphatic or aromatic moieties, W is oxygen, sulfur, or —CH2—. The additive imparts friction modification and beneficial antiwear, extreme pressure, and oxidation stability properties to the lubricating oil.
U.S. Pat. No. 6,117,826 discloses dithiocarbamyl derivatives that are useful as multifunctional additives for lubricating oils.
EP 719313 B1 broadly claims molybdenum dialkylthiocarbamates (C7-24) and alkylated diphenylamines in lubricating oils.
The disclosures of the foregoing references are incorporated herein by reference in their entirety.